NAME

srec - Motorola S-record record and file format

DESCRIPTION

Motorola S-records are a form of simple ASCII encoding for binary data.
This format is commonly used for firmware uploads to GPSes, industrial
robots, and other kinds of microcontroller-driven hardware. It has
several convenient properties, including inspectability, easy editing
with any text editor, and checksumming for verification of transmission
across noisy serial lines.
An S-record file consists of a sequence of specially formatted ASCII
character strings. An S-record will be less than or equal to 78 bytes
in length.
The order of S-records within a file is of no significance and no
particular order may be assumed.
The general format of an S-record follows:
+-------------------//------------------//-----------------------+
| type | count | address | data | checksum |
+-------------------//------------------//-----------------------+
type
A char[2] field. These characters describe the type of record (S0,
S1, S2, S3, S5, S7, S8, or S9).
count
A char[2] field. These characters when paired and interpreted as a
hexadecimal value, display the count of remaining character pairs
in the record.
address
A char[4,6, or 8] field. These characters grouped and interpreted
as a hexadecimal value, display the address at which the data field
is to be loaded into memory. The length of the field depends on the
number of bytes necessary to hold the address. A 2-byte address
uses 4 characters, a 3-byte address uses 6 characters, and a 4-byte
address uses 8 characters.
data
A char [0-64] field. These characters when paired and interpreted
as hexadecimal values represent the memory loadable data or
descriptive information.
checksum
A char[2] field. These characters when paired and interpreted as a
hexadecimal value display the least significant byte of the ones
complement of the sum of the byte values represented by the pairs
of characters making up the count, the address, and the data
fields.
Each record is terminated with a line feed. If any additional or
different record terminator(s) or delay characters are needed during
transmission to the target system it is the responsibility of the
transmitting program to provide them.
There are 9 record types, as follows:
S0
The type of record is ´S0´ (0x5330). The address field is unused
and will be filled with zeros (0x0000). The header information
within the data field is divided into the following subfields.
1. mname is char[20] and is the module name.
2. ver is char[2] and is the version number.
3. rev is char[2] and is the revision number.
4. description is char[0-36] and is a text comment.
Each of the subfields is composed of ASCII bytes whose
associated characters, when paired, represent one byte
hexadecimal values in the case of the version and revision
numbers, or represent the hexadecimal values of the ASCII
characters comprising the module name and description.
S1
The type of record field is ´S1´ (0x5331). The address field is
interpreted as a 2-byte address. The data field is composed of
memory loadable data.
S2
The type of record field is ´S2´ (0x5332). The address field is
interpreted as a 3-byte address. The data field is composed of
memory loadable data.
S3
The type of record field is ´S3´ (0x5333). The address field is
interpreted as a 4-byte address. The data field is composed of
memory loadable data.
S5
The type of record field is ´S5´ (0x5335). The address field is
interpreted as a 2-byte value and contains the count of S1, S2,
and S3 records previously transmitted. There is no data field.
S7
The type of record field is ´S7´ (0x5337). The address field
contains the starting execution address and is interpreted as a
4-byte address. There is no data field.
S8
The type of record field is ´S8´ (0x5338). The address field
contains the starting execution address and is interpreted as a
3-byte address. There is no data field.
S9
The type of record field is ´S9´ (0x5339). The address field
contains the starting execution address and is interpreted as a
2-byte address. There is no data field.

EXAMPLE

Shown below is a typical S-record format file.
S00600004844521B
S1130000285F245F2212226A000424290008237C2A
S11300100002000800082629001853812341001813
S113002041E900084E42234300182342000824A952
S107003000144ED492
S5030004F8
S9030000FC
The file consists of one S0 record, four S1 records, one S5 record and
an S9 record.
The S0 record is comprised as follows:
· S0 S-record type S0, indicating it is a header record.
· 06 Hexadecimal 06 (decimal 6), indicating that six character pairs
(or ASCII bytes) follow.
· 00 00 Four character 2-byte address field, zeroes in this example.
· 48 44 52 ASCII H, D, and R - "HDR".
· 1B The checksum.
The first S1 record is comprised as follows:
· S1 S-record type S1, indicating it is a data record to be loaded at
a 2-byte address.
· 13 Hexadecimal 13 (decimal 19), indicating that nineteen character
pairs, representing a 2 byte address, 16 bytes of binary data, and
a 1 byte checksum, follow.
· 00 00 Four character 2-byte address field; hexidecimal address
0x0000, where the data which follows is to be loaded.
· 28 5F 24 5F 22 12 22 6A 00 04 24 29 00 08 23 7C Sixteen character
pairs representing the actual binary data.
· 2A The checksum.
The second and third S1 records each contain 0x13 (19) character pairs
and are ended with checksums of 13 and 52, respectively. The fourth S1
record contains 07 character pairs and has a checksum of 92.
The S5 record is comprised as follows:
· S5 S-record type S5, indicating it is a count record indicating the
number of S1 records
· 03 Hexadecimal 03 (decimal 3), indicating that three character
pairs follow.
· 00 04 Hexadecimal 0004 (decimal 4), indicating that there are four
data records previous to this record.
· F8 The checksum.
The S9 record is comprised as follows:
· S9 S-record type S9, indicating it is a termination record.
· 03 Hexadecimal 03 (decimal 3), indicating that three character
pairs follow.
· 00 00 The address field, hexadecimal 0 (decimal 0) indicating the
starting execution address.
· FC The checksum.

NOTES

· There isn´t any evidence that Motorola ever made use of the header
information within the data field of the S0 record, as described
above. This may have been used by some third party vendors.
· The Unix manual page on S-records is the only place that a 78-byte
limit on total record length or 64-byte limit on data length is
documented. These values shouldn´t be trusted for the general case.
· The count field can have values in the range of 0x3 (2 bytes of
address + 1 byte checksum = 3, a not very useful record) to 0xff;
this is the count of remaining character pairs, including checksum.
· If you write code to convert S-Records, you should always assume
that a record can be as long as 514 (decimal) characters in length
(255 * 2 = 510, plus 4 characters for the type and count fields),
plus any terminating character(s). That is, in establishing an
input buffer in C, you would declare it to be an array of 515
chars, thus leaving room for the terminating null character.